The production of synthetic kerosene by combined DAC with water electrolysis and biomass gasification for Rotterdam-The Hague Airport along with intermittent electricity supply

Abstract

Replacing conventional kerosene has gained interest in an effort to make aviation more sustainable. In 2018 a total of 895 million tonnes of CO2 was emitted, equivalent to 2% of global CO2 emissions. For normal passenger and cargo planes synthetic kerosene is most feasible to replace conventional kerosene, hydrogen powered or electricity driven airplanes face problems and may only be feasible for small airplanes. Increased interest in electrolysis, direct air capture (DAC) and production pathways for synthetic kerosene has encouraged development and reduced the price gap with conventional kerosene. Although small pilot plants are realized last decade, little research has been done on large-scale studies. And most research is focused on one method, while an integrated system can be promising either. This thesis focused on both topics, taking Rotterdam-The Hague Airport as reference airport. Syngas will be obtained from biomass gasification and water electrolysis with a proton exchange membrane (PEM) electrolyzer. CO2 to form CO is retrieved from a DAC plant. The syngas is converted into fuel by Fischer-Tropsch (FT) technology. Several gasification technologies were studied and the direct heated steam/oxygen fluidized bed gasifier was found to be the best option. This gasifier was built and validated according to the Institute of Gas Technology (IGT) gasifier located in Hawaii. In order to accurately estimate the behavior of the process, a steady state model is developed using Aspen Plus. Two scenarios are defined and represent the intermittent behavior of renewable electricity. The first scenario simulates high renewable electricity production, while the second scenario is driven by low supply of electricity. Biomass gasification is integrated to remain a constant syngas flow for the FT reactor and subsequent kerosene production. To reach the intended annual kerosene production of 50.000 ton, it was found that a gasifier with a maximum capacity of 100 ton/h is required. Thermal efficiencies of 35% and 33% are achieved for scenario 1 and 2 respectively, taking gasoline, diesel and waxes into account as useful side-products. Total land-area required to fulfill electricity demand equals 0.9km2 of solar panels together with a wind farm covering 3.6km2 assuming turbines of 10MW. A cost analysis has been conducted to investigate the economical feasibility of the project. The average fuel price obtained in this project reached 1.74-2.87 euro/kg, exceeding conventional fuel prices. But estimated price reductions and technical improvements for wind/solar power, PEM electrolysis and DAC decrease the fuel price to 1.49-2.78 euro/kg by 2050. In addition, carbon taxes are expected to increase hence reducing the gap between conventional and synthetic kerosene even more. Future research and development must focus on extending and improving the model to acquire more precise results. Furthermore, improvements have to be made for electrolysis and DAC plants before they are economically competitive and suitable for large scale. In conclusion, the models in this thesis have shown promising results in terms of future feasibility of large scale synthetic kerosene production in an integrated system. It has proved that when future developments are realised and DAC and PEM electrolysis have become more mature, the price gap between conventional and synthetic kerosene can be overcome and large scale projects become feasible.